We have never had a plan to "stop trying to have children" at any certain age. But I guess that is mostly because we don't "try and have children", we just let God do what He will and neither try or not try.
That being said, I am about 40 and my husband is nearly 44 and we are both about ready to be done. I love children so much. But I have had some major problems with our last four pgcies, losing one at 18wk, losing another at 8wks, and having pre-E, HELLPs, & extreemly high BP for the other two.
And, since I have ever intention of hanging around to see grandchildren, great-grandchildren, great-great-grandchildren, and great-great-great-grandchildren (yes, I plan to live until I am 150), we are seriously considering us done. Seriously enough that we are looking into permenant solutions that do not cross our line of morally or spiritually acceptable.
I guess I never really thought about an "end date" when I was young and wanted children. I do think it is funny, though, I have always (since the time I was twelve) told everyone that I wanted a dozen children. More for the shock value, because it made them stop asking dumb questions. And because that is just is a number I liked. I now have ten. So, if I do get pg again, with twins, I could have my dozen.
Anyways, I guess I would not necessarily fall into the "QF movement" any more. But then again, I have never really like catagories. I tend to do my own thing.